Fix .vercelignore to only exclude root-level Python files

.vercelignore

@@ -8,17 +8,17 @@ venv/
 env/
 ENV/
 
-# Python backend (deploy to Render, not Vercel)
-api/
-src/
-requirements.txt
-runtime.txt
-render.yaml
-pyproject.toml
-.python-version
+# Python backend at root level (deploy to Render, not Vercel)
+/api/
+/src/
+/requirements.txt
+/runtime.txt
+/render.yaml
+/pyproject.toml
+/.python-version
 
 # Testing
-tests/
+/tests/
 .pytest_cache/
 .hypothesis/
 .coverage